Internal combustion engines are well known. Those employing gasoline as fuel typically employ a number of cylinders which compress a gasoline and air mixture such that upon firing of a spark plug associated with each cylinder, the compressed mixture ignites. The expanding combustion gases resulting from the ignition move a piston within the cylinder. Upon reaching an end of its travel in one direction within the cylinder, the piston reverses direction to compress another volume of the gasoline and air mixture. The resulting mechanical energy of the moving piston can and has been harnessed for use in myriad applications, foremost among which is the propulsion of vehicles.
Another type of internal combustion engines uses natural gas as the fuel source. For example, it is known to provide a compressed natural gas engine wherein a piston reciprocates within a cylinder. A spark plug is positioned within a cylinder head associated with each cylinder and each respective spark plug is controlled by a timing circuit such that upon the piston reaching the end of its compression stroke, the spark plug fires to thereby ignite the compressed mixture.
In still further types of internal combustion engines, pre-chambers are employed in conjunction with natural gas engines. A pre-chamber is associated with each cylinder of the natural gas engine and is provided with a spark plug to initiate combustion within the pre-chamber which can then be communicated to the main combustion chamber.
Some engines may have differently shaped pistons to enhance combustion. One example of such a combustion system is disclosed in U.S. Pat. Pub. No. 2010/0326400 to Hayes Jr. The system in U.S. Pat. Pub. No. 2010/0326400 includes a combustion system with a pre-chamber adapted to cooperate with a piston in a manner that produces a highly efficient combustion process. The pre-chamber has passages that have a variable cross-section and a variable angular orientation with respect to a centerline of the pre-chamber body. The piston is provided with a number of surfaces that facilitate the flow of fuel and air within the combustion chamber. In addition, the piston surfaces are generally aligned with angles of the combustion chamber such as the angle of the intake and exhaust valves. The piston also has surfaces that are adapted to cooperate with a tip of the pre-chamber.
The improvement of the design of any particular engine is often desirable, in the form of increased engine efficiency and/or reduced emissions, especially in light of increasing fuel costs and ever more strict regulations on engine emissions. Accordingly, there is a need for improved engine systems.